In using certain types of plastic material for production of containers of various sorts intended for containing fluids such as water, an inherent problem is presented in the area of connection to such material for water flow in and out of the container. Such material as fluroethylenepolymer, for example, is often used as a bearing surface and has a very low coefficient of friction. Such material, often commercialized under the trade name Teflon, poses a serious problem when it is desired to secure a compression or gasketed type of fitting to the material. Such material is also structured for poor adhesion by various cements and epoxies which work well on other types of plastic materials.
It is important in the manufacture of plastic heat exchangers, for example, such as disclosed in U.S. patent application Ser. No. 925,025, filed July 17, 1978, and assigned to the same assignee as the present invention, that fluid such as water heated by solar energy be circulated through the heat exchanger and then returned to the collector system without fluid loss such as might be caused by leakage. It is obvious that leakage is highly undesirable and, therefore, the fitting means for coupling the water flow into and out of the heat exchanger must be such that leakage will not occur. It has been found that the most suitable plastic materials from which such conformable heat exchangers are formed are those with which conventional fittings can not be efficiently utilized.